This invention relates to pressure sensitive acrylic adhesives (PSAs) for coating onto plasticized plastic substrates (such as PVC substrates) by deposition thereon and to such pressure sensitive products made therefrom which exhibit a good balance of both good peel and sheer retention after heat aging. More in particular, this invention relates to a plasticized polymer (such as polyvinyl chloride) substrate coated with a pressure sensitive adhesive deposited thereon.
Illustratively one pressure sensitive adhesive product is a bandage. PSAs are used in bandages to make a bandage stick to the skin of a patient. The PSA is adhered to a suitable medically acceptable substrate and medication applied to the substrate on which has been deposited the PSA.
PSAs are also used with plasticized polymer substrates such as polyvinyl chloride. Polyvinyl chloride ("PVC") is a commercially available linear polymer which is rigid to a certain degree. PVC may be employed in the form of foam and function as insulation for walls, roofs, and other uses usually when the PVC has been plasticized. In this way, the PVC is made softer and more flexible through the addition of plasticizers (such as phthalic esters, phosphoric esters, esters of adipic, azelac acid and sebacic acid, fatty acid esters, epoxidized fatty acid esters, citric esters, esters of acetic, propionic and butyric acids, esters of ethyl, butyric and ethyl hexanoic acid, glycolic esters, polymeric polyester plasticizers chlorinated hydrocarbons, such as chloroparaffins, benzoic esters such as diglycol benzoate, dibenzytoluene, trimetallic esters, alkyl sulfonic esters, sulfonamides such as toluene sulfonamide and abietic esters) and PVC is then acceptable as a flexible plasticized foam. The PSA is used to adhere the plasticized PVC foam to another surface. PVC films also contain plasticizer and are used in applications such as labels, decals, signs, wallpaper, etc.
While the plasticizers impart desired softness and increased flexibility to the normally rigid PVC as in plasticized PVC foam and film, the plasticizer can have an adverse effect on a PSA which has been deposited onto plasticized PVC. This adverse impact occurs during aging such as heat aging as the PSA may have its adhesion, cohesive strength or "stick" properties undesirably reduced.
In some instances, PSAs are employed with plasticized PVC sound-deadening foam in order to enable the PVC to stick to another surface quieting sound. For example, a PSA may be employed with foamed PVC (containing plasticizer) to enable the foamed PVC to adhere to a metal surface such as in a sound deadening automobile applications or gaskets.
Until this invention, the deterioration of such "stick" properties with aging had remained a persistent problem with PSA-applied plasticized PVC foam products in that the plasticized PVC foam products lose adhesion from the surface where they have been attached or that PVC plasticized tape loses its peel adhesion and shear strength properties when stored for long periods of time rendering the tape ineffective for later use.